1. Field of the Invention
The present invention relates to a portable small-sized electronic apparatus such as a notebook type personal computer, a housing for the electronic apparatus, and a method for manufacturing the housing.
2. Description of the Related Art
In the portable electronic apparatus which is represented by a notebook-type personal computer, an electronic notebook, a pocket telephone and similar, a resin has been used for the housing which has the properties of light weight, good appearance, good insulating ability and similar.
However, about 30% of the weight of the apparatus is occupied by the housing. If the weight of the housing can be reduced, the apparatus can become lighter. For this reason, the housing has been made thinner. However, ABS resins which are usually used for the housing are hard to make thinner because of insufficient strength.
Accordingly, engineering plastics having high strength, such as aromatic polyamide or PPS resins or polymer alloys including PC-ABS resins, can be used, or a filler, such as carbon fiber, is added to the ABS resins, when the housing is molded.
However, the engineering plastics are difficult to mold thinner as compared with the ABS resins. Even if the engineering plastics are used, strength and rigidity are not enough. Also, in the case where the polymer alloys are used or the filler is added, the same problems arise.
In particular, a user may often drop the portable apparatus while carrying the same. For this reason, drop impact resistance is required, such that the apparatus is not broken, even if it is dropped at a height of about 1 m. In other words, the drop impact resistance must be such that as not only the housing, but also internal electronic parts, are not degraded if dropped.
In order to obtain such required performance, methods for forming the housing of metals are known, such as by aluminum sheet metal working, aluminum alloy die casting, Mg alloy die casting, or similar. However, the sheet metal working method is difficult to form a boss, a rib and a fitting portion. Furthermore, in the case where the aluminum alloy die casting method or similar is used, it is difficult to reduce the thickness of the housing to 1 mm or less.
In addition, there is a possibility that such a metal housing is so high in rigidity that the impact force of the housing being dropped cannot be absorbed. In other words, the housing is not, broken upon being dropped but the internal electronic parts are damaged or degraded.
Thus, the above-mentioned required characteristics of strength, moldability, impact resistance and similar cannot be completely obtained by a housing made of a single material such as a metal or a resin.
Japanese Unexamined Patent Application Nos. Hei 5(1993)-114664, Hei 5(1993)-261823 and Hei 5(1993)-269787 have disclosed the combination of a metal and a resin, for example, a laminated product of a resin layer formed on the inner face of a housing which is molded of a metal.
However, the electronic parts taught by the above-mentioned Japanese Patent Applications, are accommodated in a portable electronic apparatus at a higher density with the requirement of high performance and small size. For this reason, a structure in which heat generated from the electronic parts is efficiently discharged to the outside of the apparatus has been required.